You got the benefit simply by having the bacteria on your skin. That can mean getting the “right” bacteria into your environment should make you less prone to hay fever.

It’s just another example of how the human body is a giant information processor. Give your body the right information – in this case certain bacteria living right on us – and it responds with less allergic reactions. That’s something to think about when you douse your skin with purell.

It’s also known that kids who frequently play in the dirt experience less asthma. In animal experiments, mice given lactobacilli (bacteria from yogurt) are much harder to get depressed and show markedly diminished stress responses.

Kind of what happens to humans when we move into bright, green spaces.

Green Space and Stress

Ward Thompson’s recent research has looked at cortisol levels and green space. What she found was that the more green space people had around them, the lower the cortisol levels in their blood.

Stress hormones correlated well with how much green stood around you.

And there are many other benefits to having access to green space, especially for urban dwellers.

Benefits of Green

A now well-known Lancet study of 2008 looked at survival for poor British urbanites. One of the biggest factors related to keeping people living longer was how much green space they could access.

The epidemiology is a bit complicated. Yet what it showed was this – for the highest green space quartile versus the lowest, the rate of cardiovascular disease deaths went down by 30%.

Other studies argue that survival differences between the richest and poorest parts of the population might be halved by how much access they had to green space.

So we know some of the advantages of having green space include longer lives; less heart disease; less stress; less allergies and auto-immune disease.

Next, add to the list lower weight. Kids who had a lot of green space around weighed about 13 pounds less than kids who did not have as much access to nature and natural places of play.

Also add to the list opportunity for exercise. Another recent UK study found that among the elderly, rapid access to shops, services and green spaces doubled the number who walked at least 2.5 hours a week. Those who walk more live longer and feel better. This result is consistent with data from Rush medical school that the more people get out of their homes, the less the risk of Alzheimer’s disease.

The Nature of Survival

Humans probably are hard wired to enjoy natural settings. We use divorce and distance from the natural world – in prisons – as a form of punishment. And when people are depressed, they immediately feel better when placed within natural environments – especially ones with water.

So we have some understanding of why nature may be so healthy for us:

It makes our mood better; we feel less depressed.

Forests and natural cover decrease the risk of harsh UV light which promotes skin cancer, while still allowing in mood enhancing light.

People seem to move more in nature. The greater their physical activity, the better their health.

Bacteria and other microorganisms in natural settings modify our own immunity, appearing to decrease auto-immune disease.

People feel safer in natural settings – especially quiet ones – and may have greater opportunities for social engagement. Parents may look out more for kids other than their own, and have a better chance to meet each other, among other forms of social support.

People show lower stress responses when in nature.

Bottom Line:

We evolved in very different settings than the ones we live in. Natural settings may provide more than better mood – they may increase social cohesion, mental well-being, and long term survival.

So to improve national health, is it better for us to build parks than hospitals? Bike trails than surgicenters?

It mainly depends on whether you’re talking about health or health care.

What we want is a healthier, more independent, more self-reliant and self-sustaining population – a population that actively regenerates itself. The opportunites for that improve when you have more green space – and places to enjoy nature.

Resources are limited. The point of health care should be greater health.